Why Do We Cry While Chopping Onions? Here's the Scientific Reason and Simple Remedies

Cutting onions often brings tears to our eyes a common kitchen experience we’ve all faced. But have you ever wondered why this happens? Behind this simple act lies a fascinating and complex chemical reaction.

When we cut into an onion, its cell walls break, releasing certain enzymes and sulfur-containing amino acids. These two components react to form sulfenic acid, which then quickly converts into a volatile gas called syn-Propanethial-S-oxide. This gas spreads through the air and reaches our eyes. Once it comes in contact with the moisture in our eyes, it reacts to form a mild sulfuric acid, which causes a burning sensation. In response, our eyes produce tears to flush the irritant out.

However, not all onions are equally tear-inducing. Some varieties, like Vidalia or Walla Walla which are naturally sweeter contain lower levels of these sulfur compounds. As a result, they cause less irritation. In fact, agricultural scientists have even developed "tear-less" onions that produce very little of this irritating gas.

There are several effective home remedies that can help reduce the discomfort while cutting onions. One of the most popular techniques is chilling the onion in the fridge before chopping. The cold temperature slows down the chemical reaction, reducing the release of the irritating gas.

Using a sharp knife also helps, as it causes less cell damage, which means fewer enzymes are released. Maintaining good ventilation in the kitchen like turning on a fan or cutting onions near a window can also help disperse the gas before it reaches your eyes. Some people even wear swimming goggles while chopping onions to completely block the gas from entering the eyes. Another fun and creative hack is placing a wet paper towel next to the chopping board, which can absorb some of the gas before it gets to your face.

In short, while the tears may seem like an unavoidable part of cooking with onions, they’re actually the result of a natural chemical defense mechanism of the onion. But with a few smart tricks and a little bit of science, you can minimize or even eliminate those kitchen tears.